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LM4755: Looking out relation of Watts vs dB

Deepak C
Intellectual 360 points
Part Number: LM4755

I am designing one audio amplifier with using of LM4755.

I want to achieve 84db output BY UL Standard.

I have pre-selected speaker impedance is 8R

Max power handling capacity of speaker is 8 watts.

I could not able to figure out how much voltage applied to speaker to get 84db output.

Basically i am searching for the Watts to dB Conversion formula or relation

Thanks,

Deepak

  • 0
    TI__Guru* 84915 points

    Hi, Deepak,

    The dB units always depend of a reference.

    In power units, there are dBW and dBm units to refer the gain relationship between a 1W or 1mW.

    dBW means dB relative to 1 watt, so 0 dBW = 1 watt, -3 dBW = half watt.  +3dBW = 2 watts etc.

    dBm means dB relative to 1 milliwatt, so 0 dBm = 1 milliwatt (one thousandth of 1 watt or 0.001 watt).   Also equal to -30 dBW.

    In case of the gain in the LM4755, if you refer to dB as the device gain, you will need to calculate the output power with the output voltage generated by the 84dB gain. In other words, you will need to calculate the output voltage as (V^2) / R.

    Best regards,
    Luis Fernando Rodríguez S.